OPA2673 datasheet(23/40 Pages) TI

23 / 40 page

HIGH-SPEED ACTIVE FILTERS

HIGH-POWER TWISTED-PAIR DRIVER

Frequency(MHz)

20MHz,SECOND-ORDERBUTTERWORTH

LOW-PASSFREQUENCYRESPONSE

0.1

100

600W

20MHz,Second-OrderButterworth

Low-PassFilter

1/2

OPA2673

+10V

Power-supply

decouplingnotshown.

32.3W

105W

5kW

51W

0.1 F

40W

1/2

OPA2673

100pF

133W

0.1 F

150pF

OPA2673

www.ti.com..................................................................................................................................................... SBOS382A – JUNE 2008 – REVISED OCTOBER 2008

Where two outputs are switched (see Figure 77), the

response

plots

show,

the

OPA2673

this

output line is always under the control of one

configuration gives greater than 400MHz small-signal

amplifier

the

other

result

the

bandwidth. The capacitor values were chosen as low

make-before-break disable timing. In this case, the

as possible but adequate to override the parasitic

switching glitches for two 0V inputs drop to less than

input capacitance of the amplifier. The resistor values

20mV.

were slightly adjusted to give the desired filter

frequency

response

while

accounting

for

the

approximate 1ns propagation delay through each

channel of the OPA2673.

Wideband current-feedback op amps make ideal

elements for implementing high-speed active filters

where the amplifier is used as a fixed gain block

inside a passive RC circuit network. The relatively

A very demanding application for a high-speed

constant

bandwidth

versus

gain

provides

low

amplifier is to drive a low load impedance while

interaction between the actual filter poles and the

maintaining a high output voltage swing to high

required gain for the amplifier. Figure 78 shows an

frequencies. Using the dual current-feedback op amp

example single-supply buffered filter application. In

OPA2673, an 8VPP output signal swing into a

this case, one of the OPA2673 channels is used to

twisted-pair line with a typical impedance of 50

Ω can

set up the dc operating point and provide impedance

be realized. Configured as shown on the front page,

isolation from the signal source into the second-stage

the two amplifiers of the OPA2673 drive the output

filter. That stage is set up to implement a 20MHz,

transformer in a push-pull configuration, thus doubling

maximally flat Butterworth frequency response and

the peak-to-peak signal swing at each op amp output

provide an ac gain of +4V/V.

to 8VPP. The transformer has a turns ratio of 1.4. The

total load seen by the amplifier is 35

Ω.

The 51

Ω input matching resistor is optional in this

case. The input signal is ac-coupled to the 5V dc

Line driver applications usually have a high demand

reference voltage developed through the resistor

for

transmitting

the

signal

with

low

distortion.

divider from the +10V power supply. This first stage

Current-feedback amplifiers such as the OPA2673

acts as a gain of +1V/V voltage buffer for the signal

are ideal for delivering low-distortion performance to

where the 600

Ω feedback resistor is required for

higher gains. The example shown is set for a

stability. This first stage easily drives the low input

differential gain of 4V/V. This circuit can deliver the

resistors required at the input of this high-frequency

maximum 8VPP signal with over 200MHz bandwidth.

filter. The second stage is set for a dc gain of +1V/V,

carrying the 5V operating point through to the output

pin, and an ac gain of +4V/V. The feedback resistor

has been adjusted to optimize bandwidth for the

amplifier

itself.

the

single-supply

frequency

Figure 78. Buffered Single-Supply Active Filter

Submit Documentation Feedback

Product Folder Link(s): OPA2673

OPA2673 Datasheet(PDF) 23 Page - Texas Instruments

OPA2673 Datasheet(HTML) 23 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Datasheet Download

Link URL